I have been struggling to let go of Christianity because I have so many doubts and because I feel like it doesn't allow me to be myself and live my life. I'm also gay and I tend to look at the gay culture and see the problems within it through the lens of the religion that I grew up in. I'm in a real tug of war in my life between these two religions and I just need some advice. Gassho

Nichiren had nothing really to say about sexuality except the following. I am quoting the context of the particular statement to frame it properly:

Though the teaching I am now propagating seems limited, it is extremely profound. That is because it goes deeper than the teaching expounded by T’ien-t’ai, Dengyō, and others. It is the three important matters in the “Life Span” chapter of the essential teaching. Practicing only the seven characters of Namu-myoho-renge-kyo seems limited, but since they are the master of all the Buddhas of the three existences, the teacher of all the bodhisattvas in the ten directions, and the guide that enables all living beings to attain the Buddha way, it is profound.

The sutra states, “The wisdom of the Buddhas is infinitely profound and immeasurable.” It refers to “the Buddhas” here in the sense of all Buddhas throughout the ten directions in the three existences, from the Thus Come One Mahāvairochana of the True Word school and Amida of the Pure Land school to the Buddhas and bodhisattvas of all schools and all sutras, all Buddhas of the past, future, and present, and the present Thus Come One Shakyamuni. And the sutra speaks of the wisdom of all those Buddhas.

What is meant by this “wisdom”? It is the entity of the true aspect of all phenomena, and of the ten factors of life that lead all beings to Buddhahood. What then is that entity? It is Namu-myoho-renge-kyo. A commentary states that the profound principle of the true aspect is the originally inherent Myoho-renge-kyo. We learn that that true aspect of all phenomena is also the two Buddhas Shakyamuni and Many Treasures [seated together in the treasure tower]. “All phenomena” corresponds to Many Treasures, and “the true aspect” corresponds to Shakyamuni. These are also the two elements of reality and wisdom. Many Treasures is reality; Shakyamuni is wisdom. It is the enlightenment that reality and wisdom are two, and yet they are not two.

These are teachings of prime importance. These are also what is called “earthly desires are enlightenment,” and “the sufferings of birth and death are nirvana.” Chanting Namu-myoho-renge-kyo during the physical union of man and woman is indeed what is called “earthly desires are enlightenment,” and “the sufferings of birth and death are nirvana.” “The sufferings of birth and death are nirvana” exists only in realizing that the entity of life throughout its cycle of birth and death is neither born nor destroyed. The Universal Worthy Sutra states, “Without either cutting off earthly desires or separating themselves from the five desires, they can purify all their senses and wipe away all their offenses.” Great Concentration and Insight says, “The ignorance and dust of desires are enlightenment, and the sufferings of birth and death are nirvana.” The “Life Span” chapter of the Lotus Sutra says, “At all times I think to myself: How can I cause living beings to gain entry into the unsurpassed way and quickly acquire the body of a Buddha?” The “Expedient Means” chapter says, “The characteristics of the world are constantly abiding.” Surely such statements refer to these principles. Thus what is called the entity is none other than Namu-myoho-renge-kyo.

Earthly Desires Are Enlightenment

It sounds like you are worried about the opinions promulgated as Christianity as they pertain to you.

In Buddhism, there is reality and wisdom. Reality is the way things are, and Wisdom is the knowledge about the way things are. When you see things the way they really are, judgments about right and wrong lose their basis. Sexuality, in whatever form, what can be said? Nothing. There is only the the teaching that is understood and shared only among Buddhas.

We ordinary people are far from understanding what the Buddhas know. We are caught in a house of horrors of our own projection. By holding fast to the Buddhas, we are delivered beyond the bogeymen of our minds. The Buddha left this jewel of NMRK as the means to do this.

Showing profound compassion for those unable to comprehend the gem of the doctrine of three thousand realms in a single moment of life, the Buddha wrapped it within the five characters [of Myoho-renge-kyo], with which he then adorned the necks of the ignorant people of the latter age. The four great bodhisattvas will protect anyone who embraces the five characters as faithfully as T’ai-kung Wang and the Duke of Chou supported King Wen, and as devotedly as the Four White-Haired Elders served Emperor Hui.

Kanjin no Honzon Sho, Object of devotion for the observation of the Mind

Those who, even with distracted minds,
Entered a stupa compound
And chanted but once, “Namo Buddhaya!”
Have certainly attained the path of the buddhas.
-Lotus Sutra, Expedient Means Chapter

There are beings with little dust in their eyes who are falling away because they do not hear the Dhamma. There will be those who will understand the Dhamma.
-Ayacana Sutta